Reconfigurable circuit

ABSTRACT

A reconfigurable circuit of the present invention is characterized in being provided with: a first programmable wiring group, which is disposed in the first direction; a second programmable wiring group, which is disposed in the second direction that intersects the first direction; a first switch element array, which connects the programmable wiring groups to each other at the intersecting points of the first programmable wiring group and the branch line group of a functional block input wiring group or at the intersecting points of the branch line group of the first programmable wiring group and the functional block input wiring group; a second switch element array, which connects the programmable wiring groups to each other at the intersecting points of the first programmable wiring group and functional block output wiring; and a third switch element array, which connects the programmable wiring groups to each other at the intersecting points of the second programmable wiring group and the first programmable wiring group. The reconfigurable circuit is also characterized in being provided with a fourth switch element array, which connects the programmable wiring groups to each other at the intersecting points of the second programmable wiring group and the functional block input wiring group, and/or a fifth switch element array, which connects the programmable wiring groups to each other at the intersecting points of the second programmable wiring group and the branch lines of the functional block output wiring.

This application is a National Stage Entry of PCT/JP2011/069099 filedAug. 18, 2011, which claims priority from Japanese Patent Application2010-200433 filed Sep. 8, 2010, the contents of all of which areincorporated herein by reference, in their entirety.

TECHNICAL FIELD

The present invention relates to reconfigurable circuits using arewritable nonvolatile switching element.

BACKGROUND ART

A nonvolatile switching element has been developed recently, which canbe re-written with a small area (hereinafter, referred to as arewritable nonvolatile switching element).

As shown in FIG. 15A, a rewritable nonvolatile switching element 1includes an anode 10 of a first electrode, a cathode 12 of a secondelectrode, and an ion conductor 11 sandwiched between the twoelectrodes.

The anode 10 is an electrode which supplies a metal ion to the ionconductor 11 and is mainly composed of copper. The cathode 12 is anelectrode which does not supply a metal ion to the ion conductor 11 andplatinum or the like is utilized. The ion conductor 11 has such a natureas to move the metal ion supplied from the anode 10 and tantalum oxideor the like is utilized.

FIG. 15B shows the state that the rewritable nonvolatile switchingelement 1 is ON, that is, the conduction state between these twoelectrodes. These two electrodes become the conduction state by applyinga voltage Von to the anode 10 to and connecting the cathode 12 to theground.

FIG. 15C shows the state that the rewritable nonvolatile switchingelement 1 is OFF, that is, the cut-off state between these twoelectrodes. These two electrodes become the cut-off state by connectingthe anode 10 to the ground and applying a voltage Voff to the cathode12.

Turning the rewritable nonvolatile switching element 1 ON or OFF iscalled programming. The ON state and the OFF state of the rewritablenonvolatile switching element 1 are held even if the power supply iscut.

A programmable cell 5 is disclosed in the Patent Literature 1, whichuses the rewritable nonvolatile switching element 1 as shown in FIG. 16.A horizontal programmable wiring group 100 intersects a verticalprogrammable wiring group 200, an input wiring group 310 of a functionblock 2, and an output wiring 400 of a function block 2 at anintersecting area 5000 of these wiring groups. An intersecting point ofeach wiring is coupled with each other by a rewritable nonvolatileswitching element 1A. The adjacent horizontal programmable wiring groups100 are coupled with each other by a rewritable nonvolatile switchingelement 1B and the adjacent vertical programmable wiring groups 200 arecoupled with each other by a rewritable nonvolatile switching element1B.

The rewritable nonvolatile switching element 1A is an element in which ahorizontal wiring and a vertical wiring are connected to terminals 14and 13 of the rewritable nonvolatile switching element 1 as shown inFIG. 17A. The rewritable nonvolatile switching element 1B is an elementin which adjacent wirings are connected to the terminals 14 and 13 ofthe rewritable nonvolatile switching element 1 as shown in FIG. 17B.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open PublicationNo. 2005-101535

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

However, the circuit using the rewritable nonvolatile switching elementdescribed in patent literature 1 has a problem of a lack of routability.In other words, the input wiring group and the output wiring group ofthe function block do not have a means connecting with the verticalwiring group directly. Therefore, the order for the input wiring and theoutput wiring to connect with the vertical wiring group, it is necessaryto connect via the horizontal wiring group. As a result, the degree offreedom of the wiring connectivity declines.

The object of the present invention is to provide a reconfigurablecircuit which solves the above-mentioned problem.

Means for Solving a Problem

A reconfigurable circuit, comprising: a first programmable wiring groupdisposed in a first direction; a second programmable wiring groupdisposed in a second direction intersecting the first direction; a firstswitching element array connecting the first programmable wiring groupto branch line group of input line group of a function block at thoseintersecting points, or connecting branch line group of the firstprogrammable wiring group to the input line group of the function blockat those intersecting points; a second switching element arrayconnecting the first programmable wiring group to the output wiring ofthe function block at those intersecting points; a third switchingelement array connecting the first programmable wiring group to thesecond programmable wiring group at those intersecting points; at leastone of a fourth switching element array and a fifth switching element isdisposed; and the fourth switching element array connects the secondprogrammable wiring group to the input wiring group of the functionblock at those intersecting points, and the fifth switching elementarray connects the second programmable wiring group to the branch lineof the output wiring of the function block at those intersecting points.

Effect of Invention

According to the reconfigurable circuit by the present invention, itbecomes possible to realize a circuit with having high routability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of the programmable cell 5 in the firstexemplary embodiment.

FIG. 2 is a block diagram of the reconfigurable circuit in the secondexemplary embodiment.

FIG. 3 is a circuit diagram of the programmable cell 5 in the secondexemplary embodiment.

FIG. 4 is a circuit diagram of the programmable cell 5 in the thirdexemplary embodiment.

FIG. 5 is a circuit diagram of the programmable cell 5 in the fourthexemplary embodiment.

FIG. 6A is an example of the function block 2.

FIG. 6B is a table showing the function block and the logic function.

FIG. 7 is an example of the 3-input LUT using the rewritable nonvolatileswitching element.

FIG. 8 is a top view of the wiring layout.

FIG. 9 is a side view of the rewritable nonvolatile switching element atthe intersecting point of wirings.

FIG. 10A is a perspective view of the rewritable nonvolatile switchingelement.

FIG. 10B is a perspective view of the rewritable nonvolatile switchingelement.

FIG. 11 is a circuit diagram of the programmable cell 5 in the sixthexemplary embodiment.

FIG. 12 is a state transition diagram of the reconfigurable circuit inthe seventh exemplary embodiment.

FIG. 13A is a block diagram of the first programming block in the eighthexemplary embodiment.

A FIG. 13B is a block diagram of the second programming block in theeighth exemplary embodiment.

FIG. 14 is a circuit diagram of the programming driver 7 in the eighthexemplary embodiment.

FIG. 15A is a diagram showing a structure of the rewritable nonvolatileswitching element.

FIG. 15B is a diagram showing a structure of the rewritable nonvolatileswitching element.

FIG. 15C is a diagram showing a structure of the rewritable nonvolatileswitching element.

FIG. 16 is a circuit diagram of the programmable cell 5 described in thepatent literature 1.

FIG. 17A shows a rewritable nonvolatile switching element arrangedbetween cross wirings.

FIG. 17B shows a rewritable nonvolatile switching element betweenparallel wirings.

DESCRIPTION OF EMBODIMENTS

[First Exemplary Embodiment]

The preferred exemplary embodiment of the present invention will bedescribed below using drawings. Although, technically preferablelimitations are added in the embodiments described below to embody thepresent invention, the scope of the invention is not limited to thoseembodiments.

[Description of the structure] FIG. 1 is a block diagram of areconfigurable circuit of an exemplary embodiment of the presentinvention. The reconfigurable circuit in the present exemplaryembodiment includes a plurality of programmable cells 5.

The programmable cell 5 includes a rewritable nonvolatile switchingelement 1, a function block 2, a first programmable wiring group (ahorizontal programmable wiring group 100 in the present exemplaryembodiment), a second programmable wiring group (a vertical programmablewiring group 200 in the present exemplary embodiment), input wiringgroups 300 and 310, and output wirings 400 and 410.

The output wiring 400 of the function block 2 is programmably connectedto the horizontal programmable wiring group 100 via rewritablenonvolatile switching element group 21. On the other hand, an outputwiring 410 of the function block 2 is programmably connected to thevertical programmable wiring group 200 via rewritable nonvolatileswitching element group 22. The output wiring 410 is a branch line ofthe output wiring 400.

The input wiring group 310 of the function block 2 is programmablyconnected to the horizontal programmable wiring group 100 via rewritablenonvolatile switching element group 61. The input wiring group 300 isprogrammably connected to the vertical programmable wiring group 200 viaa rewritable nonvolatile switching element group 62. The input wiringgroup 310 is branch lines of the grouped input wiring group 300.

The horizontal programmable wiring group 100 and the verticalprogrammable wiring group 200 are connected via a rewritable nonvolatileswitching element group 63.

[Description of the effect] The semiconductor integrated circuitdescribed in the patent literature 1 does not have the means forconnecting the input wiring group and the output line of the functionblock 2 to the vertical wiring group directly, and thus those areconnected with each other via the horizontal wiring group. Therefore,there is a problem of a lack of routability.

The programmable cell 5 in the present exemplary embodiment is furtherprovided with the rewritable nonvolatile switching element groups 62 and22 newly. The rewritable nonvolatile switching element group 62 connectsthe input wiring group 300 to the vertical programmable wiring group200. The rewritable nonvolatile switching element group 22 connects theoutput line 410 to the vertical programmable wiring group 200.

By the above configuration, it is possible in the programmable cell 5 toconnect the vertical programmable wiring group 200 to the input linesand the output line of the function block 2 directly. Thus, it ispossible to increase the flexibility of wiring design and to realizehigh routability.

In the present exemplary embodiment, the description has been made forthe structure in which both of the rewritable nonvolatile switchingelement groups 62 and 22 are provided; a structure is also acceptable inwhich only one of them is provided.

[Second Exemplary Embodiment]

Concerning the second exemplary embodiment, FIG. 2 is a block diagramshowing the structure of a reconfigurable circuit of the presentexemplary embodiment.

[Description of the structure] As shown in FIG. 2, a reconfigurablecircuit of the present exemplary embodiment includes a horizontal wiringgroup 1000, a vertical wiring group 2000, a first programming block7000, and a second programming block 6000. The other structure andconnection relationship of the present exemplary embodiment are the sameas those of the first exemplary embodiment. In other words, thereconfigurable circuit of the second exemplary embodiment includes theprogrammable cell 5, the rewritable nonvolatile switching element 1, thefunction block 2, the horizontal programmable wiring group 100, thevertical programmable wiring group 200, the input wiring groups 300 and310, and the output wiring groups 400 and 410.

The reconfigurable circuit in the present exemplary embodiment has aplurality of programmable cells 5. The programmable cells 5 are arrangedin a matrix in a plane. It is possible for the matrix to have any arraysize (the number of rows and the number of columns). The programmablecells 5 lying next to each other on right and left are coupled with eachother by the horizontal wiring group 1000. The programmable cells 5lying next to each other on top and bottom are coupled with each otherby the vertical wiring group 2000.

The first programming block 7000 is disposed in the end of each columnof a matrix of the programmable cell 5. The first programmable cell 7000is connected to the programmable cell 5 via the first programming wiringgroup 700.

Similarly, the second programming block 6000 is disposed in the end ofeach row of a matrix of the programmable cell 5. The second programmablecell 6000 is connected to the programmable cell 5 via the secondprogramming wiring group 600.

The plurality of first programming blocks 7000 and the plurality ofsecond programming blocks 6000 are connected by a state detection line500, and the state detection line 500 is connected to a programmingcontroller 9.

As shown in FIG. 3, the programmable cell 5 in the present exemplaryembodiment is provided with a horizontal programming transistor group31, a vertical programming transistor group 32, an input programmingtransistor group 30, and an output programming transistor 33.

The drain terminal of each transistor of the horizontal programmingtransistor group 31 is connected to each wiring of the horizontalprogrammable wiring group 100, respectively. The source terminal of eachtransistor of the horizontal programming transistor group 31 isconnected to a horizontal programming line 71.

The drain terminal of each transistor of the vertical programmingtransistor group 32 is connected to each wiring of the verticalprogrammable wiring group 200, respectively. The source terminal of eachtransistor of the vertical programming transistor group 32 is connectedto a vertical programming line 72.

The drain terminal of each transistor of the input programmingtransistor group 30 is connected to each wiring of the input wiringgroup 300 of the function block 2, respectively. The source terminal ofeach transistor of the input programming transistor group 30 isconnected to an input programming line 70.

The drain terminal of the output programming transistor 33 is connectedto the output wiring 400 of the function block 2. The source terminal ofthe output programming transistor 33 is connected to the inputprogramming line 70. While the source terminal is connected to the inputprogramming line 70 in FIG. 3, it is not limited to it, it is possibleto be connected to another programming line.

The gate terminal of each of programming transistors from 30 to 33 (agate terminal 93 of the output programming transistor 33, for example)is controlled by the programming controller 9.

The rewritable nonvolatile switching element group 51 connects thehorizontal programmable wiring group 100 to the adjacent horizontalprogrammable wiring group 100 programmably. Similarly, the rewritablenonvolatile switching element group 52 connects the verticalprogrammable wiring group 200 to the adjacent vertical programmablewiring group 200 programmably.

[Description of the action] Next, a programming example of therewritable nonvolatile switching element 1 in the present exemplaryembodiment will be described.

As shown in FIG. 3, in the case where a rewritable nonvolatile switchingelement 1 a in the rewritable nonvolatile switching element group 61 isprogrammed to ON, programming transistors 31 a and 30 a are turned on,and other programming transistors are turned off.

Next, when the input programming line 70 is set at an ON voltage Von andthe horizontal programming line 71 is set at 0 V, the rewritablenonvolatile switching element 1 a becomes the ON state after the elapseof a certain period of time. To prevent programming by mistake to anunintended rewritable nonvolatile switching element 1, it is desirableto set a non-use programming line at half the voltage of Von forprecharge.

Also, to change the rewritable nonvolatile switching element 1 a intoOFF state, the input programming line 70 should be set at 0 V and thehorizontal programming line 71 should be set at Voff of the OFF voltage.

In FIG. 3, each wiring segment of the horizontal programmable wiringgroup 100 is connected to the vertical programmable wiring group 200 viathe rewritable nonvolatile switching element group 63. Each wiringsegment of the horizontal programmable wiring group 100 is connected tothe input wiring group 310 via the rewritable nonvolatile switchingelement group 61. If performing programming, it is desirable to set onlyone rewritable nonvolatile switching element 1 at ON state. In otherwords, it is possible to prevent an erroneous operation of programmingand to perform highly reliable and stable connection by not setting morethan one rewritable nonvolatile switching element 1 which are connectedto the same wiring at ON state.

In FIG. 3, each wiring segment of the vertical programmable wiring group200 is connected to the horizontal programmable wiring group 100 via therewritable nonvolatile switching element group 63. Each wiring segmentof the vertical programmable wiring group 200 is connected to the inputwiring group 300 via the rewritable nonvolatile switching element group62. If performing programming, it is desirable to set only onerewritable nonvolatile switching element 1 at ON state. In other words,it is possible to prevent an erroneous operation of programming and toperform highly reliable and stable connection by not setting more thanone rewritable nonvolatile switching element 1 which are connected tothe same wiring at ON state.

Also, in FIG. 3, each wiring segment of the input wiring group 310 isconnected to the horizontal programmable wiring group 100 via therewritable nonvolatile switching element group 61. Further, each wiringsegment of the input wiring group 300 is connected to the verticalprogrammable wiring group 200 via the rewritable nonvolatile switchingelement group 62. If performing programming, it is desirable to set onlyone rewritable nonvolatile switching element 1 at ON state. In otherwords, it is possible to prevent an erroneous operation of programmingand to perform highly reliable and stable connection by not setting morethan one rewritable nonvolatile switching element 1 which are connectedto the same wiring at ON state.

Further, In FIG. 3, the output wiring 400 is connected to the horizontalprogrammable wiring group 100 via the rewritable nonvolatile switchingelement group 21. The output wiring 410 is connected to the verticalprogrammable wiring group 200 via the rewritable nonvolatile switchingelement group 22. If performing programming, it is desirable to set onlyone rewritable nonvolatile switching element 1 at ON state. In otherwords, it is possible to prevent an erroneous operation of programmingand to perform highly reliable and stable connection by not setting morethan one rewritable nonvolatile switching element 1 which are connectedto the same wiring at ON state.

[Description of the effect] In the programmable cell 5 by disposing therewritable nonvolatile switching element groups 62 and 22 newly, itbecomes possible to connect the vertical programmable wiring group 200to the input and output of the function block 2 directly. Thus, it ispossible to increase the flexibility of wiring design and to realizehigh routability, as is the case with the first exemplary embodiment.

Since the rewritable nonvolatile switching element 1 has a very smallarea, even if the number of the elements increases, it does not affectthe area of the whole circuit. On the other hand, since a programmingtransistor has a very large area, the number of them dominates thecircuit area. Because addition of the rewritable nonvolatile switchingelement groups 62 and 22 do not require additional programmingtransistors, the area of the whole circuit hardly increases, and thus itis possible to realize high routability,

[Third Exemplary Embodiment]

Next, the third exemplary embodiment will be described.

[Description of structure] As shown in FIG. 4, the different point ofthe present exemplary embodiment from the second exemplary embodiment isthat rewritable nonvolatile switching element groups 41 and 42 aredisposed. The other structure and connection relationship of the presentexemplary embodiment are the same as those of the second exemplaryembodiment.

A programmable cell 5 of the present exemplary embodiment is providedwith the rewritable nonvolatile switching element group 41 in thehorizontal programmable wiring group 100. The rewritable nonvolatileswitching element group 41 has a function to set an unused wiring at alogical value and prevent an unused line from becoming a floating wiringby supplying a logical value of 0 or 1 to the horizontal programmablewiring group 100 from a horizontal fixed value programmable wiring 81.

The cathodes of the rewritable nonvolatile switching element group 41are connected to each wiring of the horizontal programmable wiring group100, respectively. The anodes 10 of the rewritable nonvolatile switchingelement group 41 are connected to the horizontal fixed value programmingline 81.

Further, the programmable cell 5 of the present exemplary embodiment isprovided with the rewritable nonvolatile switching element group 42 inthe vertical programmable wiring group 200. The rewritable nonvolatileswitching element group 42 has a function to set an unused line at alogical value and prevent an unused line from becoming a floating wiringby supplying a logical value of 0 or 1 to the vertical programmablewiring group 200 from a vertical fixed value programmable wiring 82.

The anodes 10 of the rewritable nonvolatile switching element group areconnected to each wiring of the vertical programmable wiring group 200,respectively. The cathodes of the rewritable nonvolatile switchingelement group are connected to the vertical fixed value programming line82.

[Description of the action] An example of programming of the rewritablenonvolatile switching element groups 41 and 42 will be described.

If a rewritable nonvolatile switching element 1 b in the rewritablenonvolatile switching element group 41 is set at ON atate, a programmingtransistor 31 a is turned on and the other programming transistors areturned off.

Next, if the horizontal fixed value programming line 81 is set at an ONsetting voltage Von and the horizontal programming line 71 is set at 0V, the rewritable nonvolatile switching element 1 b becomes an ON stateafter the elapse of a certain period of time.

At this time, to prevent an unintended rewritable nonvolatile switchingelement 1 from being programmed, it is desirable to set a non-useprogramming wiring at half the voltage of Von for precharge. In order tochange the rewritable nonvolatile switching element 1 b into OFF state,the horizontal fixed value programming line 81 should be set at 0 V andthe horizontal programming line 71 should be set at an OFF voltage V.

[Description of the Effect] Generally, there are some unusedprogrammable wirings in a reconfigurable circuit. Without any process,an unused programmable line will be floating line whose electricpotential is unfixed because of nothing to driven it. It is desirable toeliminate a floating line because it causes a problem such as increasingpower consumption and the like.

Methods are known by which it becomes possible to prevent a programmableline from becoming a floating line by connecting pull-up resistor or abus holder. However, those methods have a problem that the area and theelectric power consumption enlarge and wiring delay increases.

The programmable cell 5 of the present exemplary embodiment isprogrammed to change the rewritable nonvolatile switching element intoan ON state which is connected to an unused wiring segment among therewritable nonvolatile switching element group 41 and the rewritablenonvolatile switching element group 42.

An unused line segment does not become a floating line because it can befixed to a predetermined logical value, if a logical value of 0 or 1 issupplied to it from the horizontal fixed value programming line 81 andthe vertical fixed value programming line 82.

In the above method, the rewritable nonvolatile switching element 1 tosupply fixed value is in OFF state in the wiring segments except therewritable nonvolatile switching element group 41 or 42. Therefore, thepower consumption and the increase in delay is very small.

Also, the area of the whole circuit hardly increases because therewritable nonvolatile switching element 1 is very small. Further, it isnot necessary to add a new programming transistor even if the rewritablenonvolatile switching element groups 41 and 42 are added newly.Therefore, it is possible to realize a floating line prevention circuiton the small area.

[Fourth Exemplary Embodiment]

Next, the fourth exemplary embodiment will be described.

[Description of structure] As shown in FIG. 5, the different point ofthe present exemplary embodiment from the second exemplary embodiment isthat rewritable nonvolatile switching element groups 40 and 43 aredisposed. The other structure and connection relationship of the presentexemplary embodiment are the same as those of the second exemplaryembodiment.

The programmable cell 5 of the present exemplary embodiment is providedwith the grouped rewritable nonvolatile switching element group 40 inthe input line group 300. The rewritable nonvolatile switching elementgroup 40 has the function to set a fixed logical value 0 to the inputline group 300 programmably.

Also, the programmable cell 5 of the present exemplary embodiment isprovided with the rewritable nonvolatile switching element group 43 inthe input line group 300. The rewritable nonvolatile switching elementgroup 43 has the function to set a fixed logical value 1 to the groupedinput line group 300 programmably.

The cathode of each element the rewritable nonvolatile switching elementgroup 40 is connected to each line of the input line group 300respectively, and the anode 10 is connected to an input logical-value-0programming line 80.

The rewritable nonvolatile switching element group 40 is programmed thatthe rewritable nonvolatile switching element 1 is into the ON state,which is associated with a line segment to be desired to set fixedlogical value to 0 among the input line group 300. Then, a desiredwiring segment of the grouped input line group 300 can be set to fixedlogical value 0 by setting the input logical-value-0 programming line 80at the logical value 0.

In the rewritable nonvolatile switching element group 43, the cathode ofeach element is connected to each line segment of the grouped input linegroup 300, and the anode 10 is connected to an input logical-value-1programming line 83.

The rewritable nonvolatile switching element group 43 is programmed thatthe rewritable nonvolatile switching element 1 is set at the ON state,which is associated with a line segment to be desired to set fixedlogical value to 1 among the input line group 300. Then, a desired linesegment of the input line group 300 can be set at a fixed logical value1 by setting the input logical-value-1 programming line 83 at thelogical value 1. By the above mentioned method, it is possible to setfixed logical values 0 or 1 to an optional input of the function block2.

[Description of the operation] An example of programming of therewritable nonvolatile switching element group 43 will be described. Ifsetting a rewritable nonvolatile switching element 1 c in the rewritablenonvolatile switching element group 43 at ON state, only a programmingtransistor 30 a is turned on and the other programming transistors areturned off.

If the input logical-value-1 programming line 83 is set at an ON settingvoltage Von and the input programming line 70 is set at 0 V, therewritable nonvolatile switching element 1 c becomes an ON state after athe elapse of certain period of time. At this time, preventing anunintended rewritable nonvolatile switching element 1 from programming,it is desirable to set a non-use programming line at a half the voltageof Von.

In order to set the rewritable nonvolatile switching element 1 c atturn-off state, the horizontal fixed value programming line 83 should beset at 0 V and the horizontal programming line 70 at an off voltage V.Programming of the rewritable nonvolatile switching element group 40 isin the same way.

FIG. 6A is an example of the function block 2 of FIG. 2. This is amultiplexer which outputs a 0 side input I0 to OUT in case of an inputI2 equal to 0 and outputs a 1 side input I1 to OUT in case of an inputI2 equal to 1.

The table of FIG. 6B shows a logic functions of the multiplexer in FIG.6A when fixed logical values at any one of 0, 1, or an optional inputsignal is given to input terminals I0, I1 and I2. Thus, various logicfunctions can be realized by giving a fixed logical value to the inputs.

[Description of the effect] Various logic functions can be set for theprogrammable cell 5 of the exemplary embodiment of the present inventionby providing the rewritable nonvolatile switching element group 40 andthe grouped rewritable nonvolatile switching element group 43. It is notnecessary for the rewritable nonvolatile switching element groups 40 and43 to provid an additional programming transistor, and so it is possibleto set a fixed logical value to the input line group 300 on the smallarea.

While the function block indicated in FIG. 6B is as one example offunction blocks, the function block would have various changes in formand details. For example, the number of inputs and outputs of thefunction block 2 can be changed.

[The other effects] Generally, a look-up table (hereinafter, LUT) iswidely used as the function block 2. FIG. 7 is an example of the 3-inputLUT using the rewritable nonvolatile switching element 1. The LUTdisposes an 8-input multiplexer 8 whose inputs from 0 to 7 are connectedto the rewritable nonvolatile switching element groups 45 and 46.

In each input of the circuit described in FIG. 7, it is programmed aswitching element of any one of LUT logical-value-0 rewritablenonvolatile switching element group 45 and LUT logical-value-1rewritable nonvolatile switching element group 46 to set at ON state.After performing programming of all pieces of rewritable nonvolatileswitching element 1, a LUT logical-value-0 programming line 75 is set atthe logical value 0 and making a LUT logical-value-1 programming line 76is set at the logical value 1, and then it functions as a LUT. I0, I1,and 12 become input of the function block 2, and OUT becomes output ofthe function block 2.

However, there is a problem that the area of a LUT using the rewritablenonvolatile switching element 1 becomes large. The reason is that LUTprogramming transistor group 35 and a LUT programming line 85 connectedto the former are needed for the inputs of the 8-input multiplexer 8 inorder to program the LUT. Because a programming transistor occupies alarge area, the area of this LUT will be very large.

In the programmable cell 5 of the present exemplary embodiment, variouslogic functions can be set to the function block 2 by providing therewritable nonvolatile switching element group 40 and the rewritablenonvolatile switching element group 43 for the input of the functionblock 2.

Also, because the input programming transistor group 30 already havingbeen provided can be used for programming of the rewritable nonvolatileswitching element 1, addition of a programming transistor is notnecessary. Thus, the present exemplary embodiment can realize a logicfunction setting means of a small area using the rewritable nonvolatileswitching element 1.

[Fifth Exemplary Embodiment]

Next, the fifth exemplary embodiment will be described.

As shown in FIG. 8, the different point of the present exemplaryembodiment from the second exemplary embodiment is that a line in thevertical direction is formed onto a M-th layer metal wiring 3 and a linein the horizontal direction is formed onto an M+1-th layer metal wiring4. Structure and connection relationship of the present exemplaryembodiment are the same as those of the second exemplary embodimentexcept lines and blocks listed above.

The programmable cell 5 of the present exemplary embodiment uses therewritable nonvolatile switching element 1.

For example, as shown in from FIG. 3 to FIG. 5, the rewritablenonvolatile switching element groups 61 and 62 form two-dimensionalswitch matrices, moreover both of them form different two-dimensionalswitch matrices with the rewritable nonvolatile switching element group63. Thus, not only a simple single switch matrix but plural switchmatrices existing in association with each other complicatedly areincluded on a reconfigurable circuit in the present exemplaryembodiment. Therefore, it is need to have an idea to lay out switchingelement groups compactly.

Here, wiring of the vertical direction is formed onto the M-th layermetal wiring 3 and wiring of the horizontal direction onto the M+1-thlayer metal wiring 4 in the programmable cell 5 in the present exemplaryembodiment, thus a wiring direction is changed for each layeralternately.

FIG. 8 is a diagram of the top view about a wiring layout sample. Here,the M-th layer metal wiring 3 is used for a vertical direction wiringand the M+1-th layer metal wiring 4 is used for a horizontal directionwiring. The rewritable nonvolatile switching element 1 is formed into anintersection of the horizontal direction wiring 4 and the verticaldirection wiring 3.

FIG. 9 is a diagram of the side view about an intersection of thevertical wiring direction 3 and the horizontal wiring direction 4. Therewritable nonvolatile switching element 1 including the anode 10, theion conductor 11, and the cathode 12 is formed between the verticaldirection wiring 3 and the horizontal direction wiring 4. A via 6connects the horizontal direction wiring 4 and the rewritablenonvolatile switching element 1. Because the anode 10 is often made ofcopper in the same material as a wiring, the vertical direction wiring 3can be used as the anode 10.

It is possible to suppress the cost by making the mask pattern simple,if forming all pieces of rewritable nonvolatile switching element 1 in asame structure. Actually, the anode 10 of every rewritable nonvolatileswitching element 1 is made to be in the vertical direction wiring 3side of M-th layer and the cathode 12 is made to be in the horizontaldirection wiring 4 side of M+1-th layer as an example using FIG. 9. Inaddition, it would be fair to reverse the directions of all pieces ofrewritable nonvolatile switching element 1.

FIG. 10A is a perspective view of FIG. 9. The rewritable nonvolatileswitching element 1 is formed between the horizontal direction wiring 4and the vertical direction wiring 3. The anode 10 is formed in the sideof the vertical direction wiring 3.

[Description of the effect] while plural switch matrices exist inassociation with each other complicatedly in the programmable cell 5 ofthe present exemplary embodiment, every rewritable nonvolatile switchingelement 1 is formed in the same direction. For example, wasteful pullingover of wiring can be eliminated as a whole and a compact layout can bemade, by connecting the anode 10 of every rewritable nonvolatileswitching element 1 to M-th layer vertical direction metal wiring andconnecting the cathode to M+1-th layer horizontal direction metalwiring. In this regard, however, the rewritable nonvolatile switchingelement 1 outside of an intersection of wiring of the vertical directionand the horizontal direction such as ones in the rewritable nonvolatileswitching element groups 51 and 52 are not available.

As shown in FIG. 10B, wiring connected to anode 10 and wiring connectedto the cathode 12 can be made reverse while keeping the direction of therewritable nonvolatile switching element 1 the same. FIG. 10B is aperspective view in which wiring is reversed compared with FIG. 10A.That is to say, the anode 10 is connected to the horizontal directionwiring 4 and the cathode 12 is connected to the vertical directionwiring 3.

Referring to this structure in detail, the anode 10 of the rewritablenonvolatile switching element 1 is connected to a M-th layer metalwiring 3A. Further, the M-th layer metal wiring 3A is connected to thehorizontal direction wiring 4 via a via 6B. The cathode of therewritable nonvolatile switching element 1 is connected to a M+1-thlayer metal wiring 4A. Further, the M+1-th layer metal wiring 4A isconnected to the vertical direction wiring 3 via a via 6A.

Thus, the anode 10 and the cathode of the rewritable nonvolatileswitching element 1 can be connected to opposite wiring of the exampleof FIG. 10A.

[Sixth Exemplary Embodiment]

Next, the sixth exemplary embodiment will be described.

As shown in FIG. 11, the different point of the present exemplaryembodiment from the second exemplary embodiment is that the rewritablenonvolatile switching element group 61 is different from the place andis renamed the rewritable nonvolatile switching element group 60.Structure and connection relationship of the present exemplaryembodiment are the same as those of the second exemplary embodimentexcept lines and blocks listed above.

As shown in FIG. 11, a reconfigurable circuit in the present exemplaryembodiment includes vertical direction branch lines 110 for the ofhorizontal direction programmable wiring group 100, and the verticaldirection branch line group 110 connect to the input line group 300 viathe rewritable nonvolatile switching element 60. In other words, in FIG.11, the rewritable nonvolatile switching element group 61 indicated inFIG. 2 is different from the place and is renamed the rewritablenonvolatile switching element group 60.

In the case of this structure, while the topology of the circuit is notchanged, polarity of the rewritable nonvolatile switching element group60 become reverse to the rewritable nonvolatile switching element group61 in FIG. 2, because it follows the above-mentioned optimum layout.

That is to say, the anode 10 of the rewritable nonvolatile switchingelement group 60 is connected to the vertical direction branch linegroup 110 of the horizontal direction programmable wiring group 100. Onthe other hand, the cathode of the rewritable nonvolatile switchingelement group 61 of FIG. 2 is connected to the horizontal directionprogrammable wiring group 100.

In both of FIG. 2 and FIG. 8, long-distance lines of the verticaldirection and the horizontal direction correspond to vertical directionwiring group and horizontal direction wiring group of an actual layout,respectively. Conforming to the rewritable nonvolatile switching elementgroups 60 and 61 described above to the compact layout method, suchhandling is needed. As above, a circuit diagram net list can bedetermined so that an optimum layout can be realized in the presentexemplary embodiment.

[Description of the effect] In every rewritable nonvolatile switchingelement 1 (except for the rewritable nonvolatile switching elementgroups 51 and 52) of FIG. 11, the anode 10 is connected to the verticaldirection wiring side. Thus, it is possible to design connecting andreversing the rewritable nonvolatile switching element 1 in a circuitdiagram according to a layout and it becomes possible to realize variouskinds of wiring design.

[Seventh Exemplary Embodiment]

Next, the seventh exemplary embodiment will be described.

As shown in FIG. 12, a reconfigurable circuit of the present exemplaryembodiment has an operation mode with transition among three states.Structure and connection relationship of the present exemplaryembodiment are the same as those of the first exemplary embodimentexcept lines and blocks listed above.

FIG. 12 indicates a state transition diagram of a reconfigurable circuitin the present exemplary embodiment. A reconfigurable circuit in thepresent exemplary embodiment makes transition among three states, suchas an intermediate state 8000, a programming state 8100, and anapplication state 8200.

A reconfigurable circuit in the present exemplary embodiment will be inthe intermediate state 8000, if it is powered on in the state that aconfiguration has not been performed yet. At that time, everyprogramming transistor becomes off state, and every programming driver 7outputs an intermediate voltage Vmdl. As a result, every line will beset at the intermediate voltage Vmdl and a floating line disappears.

In a case where one specific rewritable nonvolatile switching element 1is programmed, transition to the programming state 8100 is made. Theprogramming state 8100 turns on a programming transistor connected tothe rewritable nonvolatile switching element 1 of a programming targetand turns off programming transistors besides that.

In this case, the programming driver 7, connected to the anode 10 of therewritable nonvolatile switching element 1 of the programming target,outputs a voltage Von and another programming driver 7, connected to thecathode 12 of it, outputs zero voltage and thus programming of theswitching element into the ON state is made.

Every time a programming of one piece of rewritable nonvolatileswitching element 1 is completed, it returns to the intermediate state8000 and advances towards programming of a different switching elementagain.

[Description of the effect] In the programming state 8100, almost everyline of a reconfigurable circuit becomes a floating line. However,because it returns to the intermediate state 8000 every time the programof one switching element is ended, it is possible to charge all lines tothe intermediate voltage Vmdl and keep the electric potential within acertain range.

After desired programs have ended, transition to the application state8200 is made. Here, all power supply voltages are set to a normaloperation voltage Vdd, and an application circuit which has been writteninto the reconfigurable circuit by the programming can be operated.

When programmed once, it does not disappear even if the power supply iscut. Therefore, next time the power is turned on again and theapplication circuit is driven, it can be started from the applicationstate 8200 directly.

In the case where the application circuit is rewritten, transition tothe intermediate state 8000 is made, and a desired rewritablenonvolatile switching element 1 is set at ON state or OFF state. Whenperforming OFF state setting, transition to the programming state 8100is made, the output voltage of the programming driver 7 connected to thecathode of a rewritable nonvolatile switching element 1 of the programtarget is set to Voff, and the output voltage of a programming driver 7connected to the anode 10 to 0 V.

[Eighth Exemplary Embodiment]

Next, the eighth exemplary embodiment will be described.

Next, a programming block in a reconfigurable circuit of the presentexemplary embodiment will be described. Structure and connectionrelationship of the present exemplary embodiment are the same as thoseof the second exemplary embodiment except lines and blocks listed above.

[Description of the structure] FIG. 13A is a block diagram of the firstprogramming block 7000 in FIG. 2. The first programming block 7000includes programming drivers 7 a, 7 b, 7A, 7B, and 7C, and the TESTterminal of each programming driver 7 is connected to the statedetection line 500.

Each output PV of the programming drivers 7 a, 7 b, 7 c, 7A, 7B, and 7Cdrives the input programming line 70, the horizontal programming line71, the input logical-value-0 programming line 80, the inputlogical-value-1 programming line 83, and the horizontal fixed valueprogramming line 81, respectively.

FIG. 13B is diagram indicating a block diagram of the second programmingblock 6000 in FIG. 2. The second programming block 6000 includesprogramming drivers 7 d and 7D, and the TEST terminal of eachprogramming driver 7 is connected to the state detection line 500.

Each output PV of programming driver 7 d and 7D drives the verticalfixed value programming line 82 and the vertical programming line 72,respectively.

The first programming line group 700 of FIG. 2 corresponds to theprogramming line groups 70, 71, 80, 83, and 81 of FIG. 5. The secondprogramming line group 600 of FIG. 2 corresponds to the programming linegroups 72 and 82 of FIG. 5.

Next, a circuit diagram of each programming driver 7 will be describedusing FIG. 14.

The programming driver 7 selects one from at least three kinds of powersupply voltages such as Von, Voff, Vmdl, and a ground 0 V and outputs itto PV. Or, the whole voltage selection transistor group 36 is turnedoff, it is to be made for the PV in the high impedance state.

Which of these states is outputted by a programming driver 7 is decidedby the signal given to voltage selection line group 96. This signal isbased on a signal outputted from the programming controller 9 of FIG. 2.In other words, which of the voltages is outputted is decided by theprogramming controller 9.

When the voltage outputted to PV is 0 V, a test selection transistor 34is turned on, and the voltage of PV is outputted to a TEST terminal. Inorder to program only one rewritable nonvolatile switching element 1 ata time, only one among all pieces of programming driver 7 outputs 0 V.

That is, only one TEST terminal is enabled, and the other TEST terminalswill be in the high impedance state (a TEST selection transistor becomesoff). Because the resistance of the rewritable nonvolatile switchingelement 1 differs greatly between the ON state and the OFF state,electric potentials of the terminal PV of a programming driver 7, whichoutputs 0 V, are also different between them.

That is to say, although it is approximately 0 V in the OFF state, itbecomes of an electric potential more definitely higher than that in theON state. The difference in these electric potentials is transmitted tothe programming controller 9 from the TEST terminal through the statedetection line 500. By this, the programming controller 9 detectswhether desired programming has been performed or not.

Further, because a voltage is applied to the rewritable nonvolatileswitching element 1 via a programming transistor, a voltage that islower than the original voltage by the programming transistor thresholdvoltage Vth of the programming transistor is added. Therefore, thevoltages Von and Voff given from outside should be given a voltage ofVth higher than the ON voltage and the OFF voltage of the rewritablenonvolatile switching element 1.

In the intermediate state 8000, a half of the ON voltage is given to therewritable nonvolatile switching element 1. Therefore, it is desirableto make the external source voltage Vmdl be sum of the half of ONvoltage and the half of Vth. In general, Von is higher than Voff, andthe both voltages are different from each other. In addition, the OFFcurrent for programming the rewritable nonvolatile switching element 1to the OFF state is larger than the ON current for programming it to theON state.

Thus, regarding the ON setting and OFF setting, not only polarities ofvoltages applied to the rewritable nonvolatile switching element 1 arereversed from each other, but also voltage values and current values aredifferent from each other. The programming driver 7 of FIG. 14 can applythree different kind voltages, and can set an electric currentoptionally for each power supply by adjusting each transistor width ofthe grouped voltage selection transistor group 36.

An example is indicated in the programmable cell 5 of FIG. 2, in whichthe horizontal programmable line group 100 includes four wiring segment,the vertical programmable line group 200 includes three wiring segments,the number of inputs of the function block 2 is three, and the number ofoutputs of the function block 2 is one and these numbers may beoptional. While an example is shown, in which the length of each linesegment is equal to that of one programmable cell 5, the wiring lengthis not limited to this.

[Description of the effect] There is a problem that a reconfigurablecircuit using the rewritable nonvolatile switching element 1 can useonly one kind programming voltage generally. In other words, it isassumed that voltages of the ON setting and the OFF setting of therewritable nonvolatile switching element 1 are the same while theirpolarities are reversed from each other. However, Von and Voff are notnecessarily the same generally, and thus an ON setting current and anOFF setting current are often times different. Further, because a statebesides the ON setting and the OFF setting is also needed in theprogramming process, there is a problem that handling of various kindsof programming state 8100 is not possible.

A reconfigurable circuit using the rewritable nonvolatile switchingelement 1 in the present exemplary embodiment includes a function tooutput an ON setting voltage and an OFF setting voltage of therewritable nonvolatile switching element 1, an intermediate voltage, and0 V to the programming driver 7. Also, regarding the above outputvoltages, an electric current can be set for each power supply by anadjustment of a transistor width.

By the aforementioned configurations, appropriate ON setting conditionsand OFF setting conditions can be realized and reliable programming ofthe rewritable nonvolatile switching element 1 can be performed.Further, by having the intermediate voltage output function, erroneousprogramming of the rewritable nonvolatile switching element 1 can besuppressed because a programmable line can be held within a desiredpotential range.

While the programmable wiring groups 100 and 200 intersect with eachother perpendicularly in the above-mentioned first to eighth exemplaryembodiments, it is not limited to this angle and it may be intersectionat any angle.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof. The invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the claims.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-200433, filed on Sep. 8, 2010, thedisclosure of which is incorporated hereby in its entirety by reference.

DESCRIPTION OF THE CODES

1, 1A, 1B, 1 a, 1 b, 1 c, 40, 41, 42, 43, 45 and 46 Rewritablenonvolatile switching element

2 Function block

3 and 3A M-th layer metal wiring

4 and 4A M+1-th layer metal wiring

5 Programmable cell

6, 6A and 6B Via

7 a, 7 b, 7 d, 7A, 7B, 7C and 7D Programming driver

8 8-input multiplexer

9 Programming controller

10 Anode

11 Ion conductor

12 Cathode

13 and 14 Terminal of the rewritable nonvolatile switching element 1

21, 22, 40, 41, 42, 43, 51, 52, 60, 61, 62 and 63 Rewritable nonvolatileswitching element group

30 Input programming transistor group

31 Horizontal programming transistor group

32 Vertical programming transistor group

33 Output programming transistor

30 a and 31 a Programming transistor

34 Test selection transistor

35 LUT programming transistor group

36 Voltage selection transistor group

70 Input programming line

71 Horizontal programming line

72 Vertical programming line

75 LUT logical-value-0 programming line

76 LUT logical-value-1 programming line

80 Input logical-value-0 programming line

81 Horizontal fixed value programming line

82 Vertical fixed value programming line

83 Input logical-value-1 programming line

85 LUT programming line

93 Gate terminal of the output programming transistor 33

96 Voltage selection line group

100 Horizontal programmable wiring group

110 Vertical direction branch lines

200 Vertical programmable wiring group

300 and 310 Input line group of the function block 2

400 and 410 Output line of the function block 2

500 State detection line

600 Second programming line group

700 First programming line group

1000 Horizontal line group

2000 Vertical line group

5000 Intersecting area

6000 Second programming block

7000 First programming block

8000 Intermediate state

8100 Programming state

8200 Application state

What is claimed is:
 1. A reconfigurable circuit, comprising: a firstprogrammable wiring group disposed in a first direction; a secondprogrammable wiring group disposed in a second direction intersectingthe first direction; a first switching element array connecting thefirst programmable wiring group to branch line group of input line groupof a function block at those intersecting points, or connecting branchline group of the first programmable wiring group to the input linegroup of the function block at those intersecting points; a secondswitching element array connecting the first programmable wiring groupto the output wiring of the function block at those intersecting points;a third switching element array connecting the first programmable wiringgroup to the second programmable wiring group at those intersectingpoints; at least one of a fourth switching element array and a fifthswitching element is disposed; and wherein the fourth switching elementarray connects the second programmable wiring group to the input wiringgroup of the function block at those intersecting points, and the fifthswitching element array connects the second programmable wiring group tothe branch line of the output wiring of the function block at thoseintersecting points.
 2. The reconfigurable circuit according to claim 1,wherein the first programmable wiring group, the input wiring group ofthe function block, and the branch line of the output line of thefunction block are formed by a first direction metal wiring disposed ina M-th layer, and wherein the second programmable wiring group, thebranch line group of the input line group of the function block, thebranch line group of the first programmable wiring group, and the outputline of the function block are formed by a second direction metal wiringdisposed in a N-th layer, the second direction metal wiring intersectingthe first direction metal wiring, and M and N being natural numbers witha difference between them equal to
 1. 3. The reconfigurable circuitaccording to claim 2, further comprising a first fixed value programmingline formed by the second direction metal wiring; and a second fixedvalue programming line formed by the first direction metal wiring,wherein an intersecting point of the first fixed value programming lineand the first programmable wiring group is connected by a sixthswitching element array, and an intersecting point of the second fixedvalue programming line and the second programmable wiring group isconnected by a seventh switching element array.
 4. The reconfigurablecircuit according to claim 2, wherein the switching element is arewritable nonvolatile switching element comprising an ion conductorsandwiched by an anode and a cathode and formed with the same polaritybetween the first direction metal wiring disposed in the M-th layer andthe second direction metal wiring disposed in the N-th layer.
 5. Thereconfigurable circuit according to claim 1, further comprising firstand second input fixed value programming lines, wherein an eighthswitching element array connects the first and second input fixed valueprogramming lines to the input wiring group of the function block atthose intersecting points.
 6. The reconfigurable circuit according toclaim 1, further comprising a first programming transistor connected tothe first programmable wiring group by a drain terminal thereof; a firstprogramming line connected to a source terminal of the first programmingtransistor; a second programming transistor connected to the secondprogrammable wiring group by a drain terminal thereof; a secondprogramming line connected to a source terminal of the secondprogramming transistor; an input programming transistor connected to theinput wiring group of the function block by a drain terminal thereof;and an input programming line connected to a source terminal of theinput programming transistor.
 7. The reconfigurable circuit according toclaim 6, wherein a programming terminal of a programming driver isconnected to each programming line, wherein the programming terminal isable to select one of states of a first power supply voltage setting theswitching element to a conduction state; a second power supply voltagesetting the switching element to a cut off state; a third voltage largerthan a half of the first power supply voltage by a half of a thresholdvoltage of the programming transistor; a ground voltage; and a highimpedance, and each programming terminal is controlled by a signaloutputted from a programming controller.
 8. The reconfigurable circuitaccording to claim 7, wherein the programming driver comprises a voltageselection transistor selecting one of the first to third power supplyvoltages and the ground voltage, and a width of the voltage selectiontransistor for selecting the first power supply voltage is smaller thana width of the voltage selection transistor for selecting the secondpower supply voltage.
 9. The reconfigurable circuit according to claim8, wherein a source terminal of a test selection transistor is connectedto the programming terminal of each programming driver, a drain terminalof the test selection transistor is connected to a state detection line,the state detection line is inputted into the programming controller,and the test selection transistor of a programming driver concerned inprogramming of the switching element among the programming driverstransmits a source voltage to a drain terminal.
 10. The reconfigurablecircuit according to claim 8, wherein the test selection transistor of aprogramming driver with the programming terminal being set at a groundvoltage among the programming drivers transmits a source voltage to adrain terminal.